DESCRIPTION: The overall goal of this project is to develop a better understanding of the functional neuroanatomy of the auditory system and how this is affected by tinnitus, sensorineural hearing loss (SNHL) and phenomena associated with SNHL such as loudness recruitment. In preliminary studies, using positron emission tomography (PET) to measure cerebral blood flow (CBF), we have identified spontaneous neural activity in the central auditory system associated with tinnitus, evidence for plastic reorganization of central auditory systems, and links between sensory-motor systems and limbic and frontal brain regions that may mediate the emotional disability associated with tinnitus. We will broaden our successful preliminary approach by using statistical parametric mapping (SPM) to map CBF to focus on 5 specific aims: 1) What is the relationship between the intensity of an external tone and the degree of activation in the auditory cortex for subjects who have: (A) normal hearing, (B) loudness recruitment and (C) loudness recruitment plus tinnitus? 2) What effects do tinnitus and SNHL have on resting neural activity and what are the effects of high-frequency SNHL and tinnitus on the cortical frequency-place map? 3) What regions of the cerebral cortex are activated in patients who can modulate the loudness or pitch of their tinnitus with an oral-facial movement or eye movements? 4) Do lidocaine and residual inhibition reduce activity in regions of the brain activated by tinnitus? 5) What is the anatomical link between tinnitus and depression? This application of advanced imaging technology to study patients with communication disorders to investigate perception, and plasticity in the central auditory system should elucidate normal sensory processing of auditory information and how this is disturbed by tinnitus and SNHL. We expect to identify neural systems mediating tinnitus and related phenomena that will lead to the development of rational therapy targeted at affected neural areas.